Spectrum adding system for electronic musical instruments



NOV. 12, 1968 KAZUO s 5 I ETAL 3,410,948

SPECTRUM ADDING'SYSTEM FOR ELECTRONIC MUSICAL INSTRUMENTS Original Filed Sept. 24, 1964 3 Sheets-Sheet 1 Fig.1.

W wZ 153 INVENTORS Kazaa ISh/bslwi Hiroshi (95am;

ATTORNEYS NOV. 12, 1968 KAZUO 5 3 5 ETAL 3,410,948

SPECTRUM ADDING SYSTEM FOR ELECTRONIC MUSICAL INSTRUMENTS 3 Sheets-Sheet 2 Original Filed Sept. 24, 1964 m; m m I b a 3 W e 0 0 I O 6 s F 1 u a 0 H .r F v v wv HHW, 6 0 0 M M M 5 w M l 1 II II lllllll WW. 2 M 8 M M M w w n m m M7 m M m m 11:! H 4 4! a M M M M h h rm m 4 e om h k M W41}. M. I a n1 nil: 4| 6 w a m a l 2 5 m ATTORNEYS NOV. 12, 1968 KAZUO |$H|BA5H| ET AL 3,410,948-

SPECTRUM ADDING SYSTEM FOR ELECTRONIC MUSICAL TNSTRUMEN'IS Original. Filed Sept. 24, 1964 3 Sheets-Sheet 3 Fig .4.

Rik)

ATTORNEYS K to AmP.

INVENTORS' Kazan Ishi bashi United States Patent 3 410,948 SPECTRUM ADDING SYSTEM FOR ELECTRONIC MUSICAL INSTRUMENTS Kazuo Ishibashi, Fuchu, Tokyo, and Hiroshi Ogawa, Yokohama, Japan, assignors to Victor Company of Japan, Limited, Kanagawa-ku, Yokohama, Japan, a corporation of Japan Continuation of application Ser. No. 398,922, Sept. 24, 1964. This application Sept. 14, 1967, Ser. No. 667,864 Claims priority, application .lapan, Sept. 30, 1963, 38/ 52,885 2 Claims. (Cl. 84--1.11)

ABSTRACT OF THE DISCLOSURE An electronic musical instrument having a master oscillator, a plurality of frequency dividing oscillators dividing the output signal generated from said master oscillator, a p urality of keying circuits for selectively passing the output signals generated from the master oscillator and frequency dividing oscillators, a plurality of low-pass filters connected with each of said keying circuits for correcting the output signal of said keying circuits in a sine or quasi sine wave, and means for adding together the output signal of said low-pass filters.

This is a continuation of application Ser. No. 398,922 filed Sept. 24, 1964, and now abandoned.

The present invention relates to a spectrum adding system and more particularly to a spectrum adding system for an electronic musical instrument.

As such kind of system for electronic musical instruments, it has heretofore been proposed to use so-called individual oscillating system and a frequency dividing oscillating system. As 'will be explained hereinafter, the individual oscillating system requires a number of stable sine wave osci'lators, whilst the frequency dividing oscillatin g system has the disadvantage that the variation in tone of the sound produced is quite poor,

The invention is intended to obviate the disadvantages of the above mentioned conventional systems.

A main object of the invention is to provide a novel and improved spectrum adding system.

Another object of the invention is to provide an electronic musical instrument adapted to produce a sound rich in the variation in tone thereof with the aid of a small number of main oscillating sources.

A further object of the invention is to provide an electronic musical instrument adapted to produce a sound having a spectrum which is the same throughout the whole range thereof, that is, a sound which does not vary in tone by the selected position of the keyboard.

A still further object of the invention is to provide an electronic musical instrument which can easily be tuned.

Another object of the invention is to obtain an electronic musical instrument by which a vibratory effect can easily be obtained.

A further object of the invention is to provide an electronic musical instrument which is cheap in price and excellent in character.

For a better understanding of the basic idea underlying the invention, the same will be explained by reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating one example of the conventional spectrum adding systems for an electronic musical instrument;

FIG. 2 is a block diagram illustrating another example of the conventional spectrum adding systems for the electronic musical instrument;

FIG. 3 is a block diagram illustrating a principle of a spectrum adding system for an electronic musical instrument according to the present invention;

FIG. 4 is a block diagram showing an input and output system for the signal in the essential part of the system shown in FIG. 3;

FIG. 5 is a block diagram showing connections between the keying circuits and the low-pass filters shown in FIG. 4; and

FIG. 6 diagrammatically illustrates an electric circuit embodying the keying circuit and the low-pass filter shown in FIG. 5.

As a conventional spectrum adding system for electronic musical instruments, there has been proposed an individual oscillating system as shown in FIG. 1.

In this system, a number of component circuits of a keying circuit 1 are connected independently and separately to each individual component oscillator of a sine wave oscillator 2.

The oscillations required for any desired musical instrument are derived from the sine wave oscillator 2 by suitably selecting a keyboard (not shown) connected to the keying circuit 1. These sine Wave outputs are added together at 3 to form a spectrum for any desired musical instrument.

This resultant wave output is supplied to an amplifier 4 where it is amplified and then supplied to a loudspeaker 5 from which is produced a desired musical sound.

The above mentioned system has the advantage that the spectrum for the desired musical instrument can uniformly be obtained throughout all ranges of the keyboard. This system, however, has many disadvantages since it requires a number of stable sine wave oscillators corresponding in number to the sound sources, resulting in difiiculties in technique, so many oscillators are present independently one from the other and the tuning thereof becomes quite difiicult, the vibration effect is not easily obtained, and the price is extremely high.

As another conventional spectrum adding system, there has been proposed a frequency dividing oscillating format system. In such system, provision is made of an oscillator 6 adapted to oscillate at one octave (twelve sounds) of the oscillations required for the musical instrument. The oscillator 6, therefore, consists of a number of component oscillators arranged independently one from the other. The oscillations up to the necessary lowest frequency thereof derived from the oscillators are divided in frequency per octave by means of a frequency divider 7. The output from the frequency divider 7 is supplied to a keying circuit 8 adapted to eflect keying by suitably selecting the keyboard. Then, the saw-tooth waves or rectangular Waves containing a higher harmonic Wave are added together and the resultant wave thus obtained is supplied to a sound filter 9 where a spectrum for the desired musical instrument is formed. The musical sound thus obtained is supplied through an amplifier 10 to a loudspeaker 11. This system has the advantage that the individual sine wave oscillator necessary for the conventional individual oscillating system can be omitted, but has disadvantages in that a musical sound having the same spectrum for all ranges of the keyboard cannot be produced, it is diflicult to produce a musical sound having a complex spectrum, and the variation in tone color is very poor.

In the system according to the invention, a rectangular or saw-tooth wave is caused to pass through a low-pass filter so as to correct the wave form into a sine or quasi sine wave having less distortion and the waves thus corrected are added together under the same condition as in a conventional individual oscillating system.

The invention will now be explained with reference to FIG. 3 in which 12 designates a master oscillator adapted to oscillate at a frequency f 13, 13, 13", 13 13 are frequency dividing oscillators adapted to oscillate at frequencies 1 lower than the frequency f of the master oscillator 12, respectively. 14 shows a keying circuit connected to the master oscillator 12 and to the frequency dividing oscillators 13-43, respectively. The keying circuit 14 is also connected to a keyboard (not shown) so that the keying circuit 14 can be operated by suitably selecting the keyboard. 15 shows a low-pass filter connected to the keying circuit 14. 16 is an amplifier and 17 is a loudspeaker.

The master oscillator 12 is caused to oscillate in a stable state at the maximum tone of one octave (twelve sounds) necessary for the musical instrument. The output of the master oscillator 12 is derived through the frequency dividing oscillator 13 at the frequency /2 R. The output thus obtained is supplied to the frequency dividing oscillator 13' from which the output is derived at the frequency A f The succeeding frequency dividing oscillators 13--13 are adapted to derive respective outputs at the frequency as shown in FIG. 3. The outputs from the master oscillator 12 and from the frequency dividing oscillators 13243 are supplied to the keying circuits 14, respectively. The wave form of these outputs at a point a is a saw-tooth or rectangular wave containing a higher harmonic, so that it is subjected to distortion. If keying is effected by selecting any desired keyboard, the same wave form as that at the point a is individually produced at a point I; of the output of the keying circuit 14 in response to the keying operation. This output is caused to pass through the low-pass filter 15 and thus a sine or quasi sine wave is produced at a point 0 of the output of the lowpass filter 15. The low-pass filter 15 may be one which is simple in construction and cheap in price. The outputs from all of the low-pass filters 15 are added together at a point 0 in the sine or quasi sine wave form, forming a spectrum for any desired musical instrument. The spectrum thus obtained is supplied through the amplifier 16 to the loudspeaker 17 from which a complex musical sound is produced.

A circuit connection between the master oscillator and the frequency dividing oscillators belonging to each musical scale and the keying and filter circuits is shown in FIG. 4. The output of the master oscillator i of the sound 0 is connected to the keying and filter circuit K-l, the output of the first frequency dividing oscillator f /2 is connected to the keying and filter circuit K-3, the output of the second frequency dividing oscillator f /4 is connected to the keying and filter circuit K-S, the output of the third frequency dividing oscillator f 8 is connected to the keying and filter circuit K-7, and the output of the fourth frequency dividing oscillator 16 is connected to the keying and filter circuit K-9, respectively. In the similar manner, the outputs of the master oscillators f of the sounds B, Ali, A Cit and the outputs of the frequency dividing oscillators f /2, f /4, f 8 of these sounds are connected to the corresponding keying "and filter circuits K-l, K-2 K9. Here, the keying and filter circuits constitute one octave by means of K-1 and K-Z. Similarly, K-3 and K-4, K and K-6, K-7 and K-S constitute one octave, respectively. In the example shown in FIG. 4, four octaves are used. In practice, however, the order of the seven octaves may be used.

A block diagram embodying one of the keying and filter circuits is shown in FIG. 5. The saw-tooth or rectangular wave is supplied to each of the keying circuits 141, 142 146 which is associated with a keyboard (not shown). The output of the keying circuit is supplied to the low-pass filter having a sharp inclined flank 151, 152 155 where the output wave is corrected into the sine or quasi sine Wave. An example of the circuit embodying a part of the keying circuits 141 146 is shown in FIG. 6. The rectangular or saw-tooth wave derived from the frequency dividing oscillator is always supplied to a point e. For example, if a key switch S of the keyboard is closed, a normal bias is applied to a transistor Tr which then becomes conductive and the output thereof appears at a point 1. This output is caused to pass through three stages of the low-pass filters where it is corrected in the wave form into the sine or quasi sine wave which then appears at the point 0 as shown in FIG. 5. In this case, it is preferable to use one filter for each keying circuit. In the present example, however, adjacent sound scales are commonly used and five filters 151, 152 155 are used for six sounds having half octave, that is, three stages of the filters per one sound are used for the purpose of improving the filter effect. The low-pass filter is a simple filter consisting of R C as shown in FIG. 6.

All of the outputs from each keying circuit are coupled at the point 0 and supplied to the amplifier 16 as shown in FIG. 3. Thus, the rectangular or saw-tooth wave outputs from the frequency dividing oscillators are added together at the point 0 to form the sine or quasi sine wave. As seen from the above, the spectrum adding system according to the invention makes it possible to provide the keyboard with key switches for the frequency dividing oscillator, the frequency of which being twice, thrice, fourth eleventh times the base frequency, and add a desired spectrum for any desired musical instrument by the selection of the key switches.

It may 'be clear that the invention is not restricted to the embodiments described and that many variations are possible for those skilled in the art without leaving the scope of the invention.

What is claimed is:

1. An electronic musical instrument comprising a plurality of master oscillators the combined frequencies of which cover one octave, a plurality of series of frequency dividers generating signals in frequencies dividing the frequencies of each of said master oscillators per octave successively, a plurality of keying circuits operatively connected to the output of each of said master oscillators and each of said frequency dividers, keyboard means operatively connected to control said keying circuits to selectively pass the output signals from said master oscillators and said frequency dividers, a plurality of lowpass filter means operatively connected to each of said keying circuits, said filter means converting the output signals of said frequency dividers from rectangular waves and saw-tooth waves including higher harmonics into substantially sine waves of fundamental frequencies, and means for adding together the output signals from said low-pass filter means to thereby produce a tone.

2. An electronic musical instrument comprising a plurality of master oscillators the combined frequencies of which cover one octave, a plurality of series of frequency dividers generating signals in frequencies dividing the frequencies of each of said master oscillators per octave successively, a plurality of keying circuits operatively connected to the output of each of said master oscillators and each of said frequency dividers, keyboard means operatively connected to control said keying circuits to selectively pass the output signals from said master oscillators and said frequency dividers, multistage low-pass filter means including at least a plurality of first stage low-pass filter means connected directly with every adjacent two said keying circuits and second stage low- 5 6 pass filter means operatively connected for filtering a References Cited numiber 0f the outputs of said first low-pass filter means, UNITED STATES PATENTS sald multistage low-pass filter means converting the output signals of said frequency dividers from rectangular 2,233,948 3/1941 P 841-26 X Waves and saw-tooth Waves including higher harmonics 5 2,986,964 6/1961 Blssonette X into substantially sine waves of fundamental frequencies, and means for adding together the output signals from JOHN HEYMAN Prlmary Exammer' said low-pass filter means to thereby produce a tone. DONALD D. FORRER, Assistant Examiner. 

